Epoxide resin compositions and method

ABSTRACT

A method of improving epoxy resin compositions to provide a cured resin having improved glass transition temperature and toughness characteristics is provided. The method includes providing in an epoxy resin composition an effective amount of a 9,9-bis(hydroxphenyl)fluorene composition. The fluorene component acts as a chain extension agent and provides for increased glass transition temperature and less cross-link density. As a result, improved toughness occurs. In preferred applications a toughening agent is provided in the resin composition, to further enhance toughness. Preferred resin compositions, cured resins and methods of providing improved cured resins are also provided.

FIELD OF THE INVENTION

The present invention relates to epoxy resin compositions, and inparticular to epoxy resin compositions which when cured exhibitpreferred physical and chemical characteristics. Specifically, epoxyresin compositions according to the invention cure to exhibit relativelyhigh glass transition temperatures and high ductility or toughnesscharacteristics.

BACKGROUND OF THE INVENTION

Epoxy resins are monomers or pre-polymers that react with curing agents,through the epoxy functional ring, to yield high performance curedresins. Such resins, for example, are widely utilized as: protectivecoatings for electrical insulation; composite matrix resins; and, asstructural adhesives, due to their combination of desired chemical andphysical characteristics, such as thermal and chemical resistance,adhesion retention and abrasion resistance.

Epoxy resins generally include a plurality of epoxy or oxirane groups.The epoxy groups can react to form a network, typically either throughhomopolymerization or through addition polymerization with an epoxycuring agent. As used herein, the term "epoxy curing agent" is meant torefer to an agent (or mixture of agents) having three or more reactivesites available for reaction with oxirane groups. As a result of such astructure, an epoxy curing agent can generate a network; i.e. asignificantly cross-linked system.

Epoxy curing agents are to be distinguished from compounds referred toherein as merely chain extension agents. As used herein, the term "chainextension agent" is meant to refer to a compound which has only 2 sitescapable of reaction with oxirane groups. During polymerization, a chainextension agent will typically become lodged between epoxy resin chains,extending same. Little cross-linking occurs, however, since the chainextension agent does not include a third reactive site.

As used herein, the term "catalyst" is meant to refer to a compoundcapable of catalyzing polymerization of a di-epoxy resin-compound withsubstantial networking or cross-linking. Generally, this occurs throughgeneration of anionic or cationic polymerization reactions, typicallyinvolving the oxirane moiety. During polymerization in the presence of acatalyst, a di-epoxy compound is capable of reacting at four sites, andthus substantial cross-linking can result.

An example of an epoxy curing agent is a diprimary amine, which iscapable of reacting with four epoxy groups. Typical chain extensionagents include diphenols, such as resorcinol or bisphenol A. Catalystsinclude Lewis acids, tertiary amines and imidazoles.

Throughout this specification, "catalysts" and "epoxy curing agents"will be referred to collectively as "epoxy curatives" or "curatives".

Frequently, it is desired that the cured product have a relatively highglass transition temperature (Tg). The glass transition temperature isthe temperature at which the cured resin changes from a relativelystrong, high modulus, hard, vitreous state to a low modulus, pliable,elastic state. In general, if it is intended that the cured resin bestrong at relatively high temperatures, then a relatively high glasstransition temperature will be necessary.

A commonly used method of obtaining an improved or higher glasstransition temperature is through preparation of a cured resin having ahigh concentration or degree of cross-linking, or a relatively highconcentration of polar groups. A method of achieving high cross-linkingis to use an epoxy curing agent having a high level of functionality, oran active homopolymerization agent. In U.S. Pat. No. 4,331,582,incorporated herein by reference, it is taught thatbis[4-(N,N-diglycidylamino)phenyl]methane (TGDDM) may be cured withdi(4-aminophenyl)sulfone (DDS), to yield a cured resin having a highcross-link density.

Resins having a high cross-link density have several shortcomings. Forexample, such materials are typically very brittle, and thus undesirablefor many applications. That is, the materials are not very tough orductile. Also, especially if a high concentration of polar groups isutilized to help obtain high glass temperature, the cured polymer maynot be satisfactorily stable to moisture.

Generally, to obtain a relatively tough cured resin, it is desired toutilize a composition which exhibits a high degree of cure, and forwhich, following curing for a reasonably short period of time, a veryhigh percentage of epoxy resin will have reacted to form extended chainswithin the polymer network. Generally, a high concentration of chainextension agent, such as diphenol, can be utilized to accomplish a highdegree of cure. Examples are indicated in U.S. Pat. Nos. 2,934,521 and3,056,762, the disclosures of which are incorporated herein byreference. A problem with such conventional uses of chain extensionagents is that while the resulting resins exhibit a relatively highdegree of curing and toughness or ductility, generally the glasstransition temperature for the cured product is relatively low, becauseof low cross-link density.

A substituted fluorene, in particular9,9-bis(4,4'-hydroxyphenyl)fluorene, is known to react with conventionalepoxy polymers, see for example Holloway, Jeffrey G., Low FlammabilityEpoxy Polymers Via 9,9-Bis(4,4'-Aminophenyl)Fluorene, p. 14, Master'sThesis, San Jose State U. (1984), incorporated herein by reference. Aclass of compounds which include the above-named substituted fluorene isused, as described below, in preferred embodiments of the presentinvention, to yield advantages in certain resin compositions.

What has been needed has been a readily curable epoxy resin compositionfor providing a cured resin having both high glass transitiontemperature and improved toughness or ductility; i.e. achievement ofhigh glass transition temperature without high cross-link density orpolarity which may cause brittleness and/or instability to water.Preferably, the desired features are attainable in a resin compositionreadily cured by a readily available and effective agent. Also, methodshave been needed whereby: improved or higher glass transitiontemperature for a cured resin composite can be generated withoutsubstantial loss of toughness; and/or, improved or higher toughness canbe obtained without substantial lowering of glass transitiontemperature.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a resin compositioncapable of being cured to form a resin having a relatively high glasstransition temperature with relatively high toughness.

It is another object of the present invention to provide a method bywhich an epoxy resin can be cured to a resin having a relatively highglass transition temperature and a relatively high toughness.

It is another object to the present invention to provide a method bywhich an epoxy resin composition can be improved to cure to a curedstate having improved (higher) glass transition temperature withoutsubstantial loss of toughness, and preferably with improved toughness.

It is another object of the present invention to provide a method bywhich an epoxy resin composition can be improved to cure to a curedstate having improved toughness without any substantial lowering ofglass transition temperature, and preferably with higher glasstransition temperature.

It is yet another object of the present invention to provide a preferredcured resin exhibiting relatively high toughness and relatively highglass transition temperature, formed through the utilization of abis(hydroxyphenyl) substituted fluorene compound as a chain extensionagent, preferably in conjunction with an epoxy curative, such as acuring agent or catalyst.

Another object of the invention is to provide a preferred curable epoxyresin composition for use as a film adhesive.

Other objects and advantages of the present invention will becomeapparent from the following descriptions wherein are set forth by way ofillustration and example detailed embodiments of the present invention.

SUMMARY OF THE INVENTION

According to the present invention, fluorene-containing bisphenols areprovided in a resin composition with a polyepoxide to form, upon curing,a cured resin exhibiting either: improved glass transition temperature;improved toughness; or both. Generally this is accomplished through useof fluorene-containing bisphenol(s) in the presence of a conventionalepoxy curative. The terms "high glass transition temperature" or"improved glass transition temperature" as used herein are intended torefer to cured compositions whose Tg has been increased throughapplication of the present invention. The terms "high" or "improved"toughness are meant to refer to cured compositions exhibiting increasedshear strength and/or peel strength, relative to unimprovedcompositions. That is, typically conventional methods of improving glasstransition temperature involve loss of toughness. When, according to thepresent invention, an epoxy resin composition is provided with animproved glass transition temperature, through inclusion of a chainextension agent therein, without substantial loss of toughness, i.e. nogreater than about 20% lowering in shear strength, at ambienttemperature and pressure, the resin composition will be understood to beimproved. In the alternative, when an epoxy resin is provided with animprovement in toughness, through inclusion of a chain extension agenttherein, without substantial lowering of Tg (<typically about a 25°drop), the resin composition will also be understood to have beenimproved.

In preferred applications of the present invention a toughening agent isused in combination with a chain extension agent to achieve a uniqueimprovement in toughness, along with an improvement in glass transitiontemperature. This will be understood from examples described herein.

For preferred compositions according to the present invention, the glasstransition temperature is at least 120° C., and the fracture energy atleast about 100 Joules/m². An improvement in Tg of at least 25° C.without any substantial (typically greater than about 20%) loss intoughness as evidenced by peel strength and/or fracture energy generallydefines a noticeably improved composition according to the invention. Inthe alternative, an improvement of at least about 20 Joules/m² infracture energy at ambient temperature and pressure, without anysubstantial loss (typically greater than about 25°) in Tg also generallydefines a noticeably improved composition according to the invention. Itwill be understood that the amount of Tg and fracture energy changewhich amounts to a "substantial" change will, in part, depend upon theabsolute values of the Tg or fracture energy in the unimprovedcomposition. The above stated figures are intended to berepresentational for commonly used systems.

A variety of epoxy resins may be utilized in improved resin compositionsaccording to the present invention, including both aromatic andaliphatic epoxy resins. Also, a variety of fluorene-containing bisphenolcompositions (including mixtures) may be utilized, generally includingcompounds according to the following formula: ##STR1## wherein: each R⁰and R¹ is independently selected from hydrogen and other groupssubstantially inert to the polymerization of epoxide group-containingcompounds; for example R⁰ is preferably selected from the groupcomprising: H (hydrogen), the halogens (F, Cl, Br and I); linear andbranched alkyl groups having 1-6 carbon atoms, phenyl groups, nitrogroups, acetyl groups, and trimethylsilyl groups; and, each R¹ ispreferably independently selected from the group comprising: hydrogen(H), phenyl, the halogens, and linear and branched alkyl groups having1-6 carbon atoms. When it is said that R⁰ and R¹ are "independently"selected, it is meant that there is no requirement that all R⁰ be thesame, or that all R¹ be the same. The terms "fluorene-containingbisphenol composition", "9,9-bis(hydroxyphenyl)fluorene composition" andvariants thereof are meant to refer to single compounds and mixtures ofcompounds according to the above formula.

It is noted that the diamino-analogue to the above described compound isalso a chain-extension agent. This compound and its use to improve epoxyresins is the subject of U.S. Pat. No. 4,684,678. That patent is ownedby the assignee of the present invention, Minnesota Mining andManufacturing Co., St. Paul, Minn. In general, the di-hydroxy compoundis preferred, in part because it is less reactive with epoxy compoundsthan is the diamine. That is, the resin composition is more readilystored, handled, and applied, prior to cure, when the di-hydroxy agentis used. Also, the di-hydroxy compound generally dissolves better in theresin composition mixture.

There is no universal agreement on the terminology to be utilized in thefield of epoxy resins. The term "epoxy resin" has been used to indicateboth: any molecule containing at least one group having a 3-memberoxirane ring; and, also, both uncured and cured compositions. That is,the cured resin is often referred to as an "epoxy resin" even though theepoxy groups may have been reacted and destroyed during the curingprocess.

Herein, the term "polyepoxide resin" refers to a molecule that contains,or contained prior to reaction, more than one oxirane ring. Generally,herein the term "epoxy resin composition" refers to the uncuredcomposition which, upon curing, cures to a "cured epoxy resin". When itis said herein that an epoxy resin composition "includes" or "comprises"it is meant that the composition either: comprises a mixture of thecomponents unreacted; or, includes resulting polymer or polymer materialformed from polymer-forming reaction(s) of those components, to leaveresidue(s) therefrom in the polymer; or the composition includes both.

Preferred epoxy resin compositions according to the present inventioninclude an effective amount of a toughening agent therein. A variety oftoughening agents are well-known. They generally comprise elastomermolecules and similar compounds which are incorporated into the resincomposition but which do not necessarily become chemically involved inthe curing process. That is, the compounds may sometimes remainindependent in the matrix defined by the cured resin. The presence ofthe compounds imparts preferred physical characteristics to the curedresin, relating generally to decreased brittleness and increasedtoughness. In some instances, the toughening agent may be chemicallyincorporated into the epoxy resin itself, for example as a substituenton the epoxy-containing component. An "effective" amount of a tougheningagent is an amount effective to impart an improvement in toughness tothe cured resin composition. This may be characterized as an improvementof at least about 20% in the peel strength, at ambient temperature andpressure. The term "toughening agent" and variants thereof, as usedherein, will be understood to include mixtures containing a plurality ofsuch agents.

According to the present invention, a method of improving an epoxy resincomposition, whereby a resulting cured epoxy resin is provided withimproved glass transition temperature and improved toughness, comprisesprovision of a chain extension agent comprising a 9,9-bis(hydroxyphenyl)fluorene component in an effective amount in the epoxy resincomposition. An "effective amount" of the 9,9-bis(hydroxyphenyl)fluoreneis an amount sufficient to impart improvement in Tg and/or toughness ofthe cured resin composition, as above defined. Preferably, as aboveindicated, a toughening agent is also provided.

As previously indicated, in preferred applications of the presentinvention an epoxy resin composition is provided with both: a9,9-bis(hydroxyphenyl)fluorene component; and, an epoxy curativecomponent. In this manner, the difunctional fluorene component may beused to increase epoxy resin chain length, without introduction ofincreased cross-linking. The curative, on the other hand, is used tointroduce sufficient cross-linking to result in strength and integrityof cured resin. Typically, the amount of 9,9-bis(hydroxyphenyl)fluoreneutilized is such that about 5-90% and about 9-70%, of reactive oxiranerings in the epoxy resin will react with active hydroxy-groups providedby the substituted fluorene component. Preferably less than 50% of theoxirane units are reacted with the substitute fluorene, for manyapplications. Generally, both the substituted fluorene and the epoxyresin are di-functional with respect to this reaction, thus the ratio ofreactive epoxy resin molecules to reactive fluorene compound should bebetween about 1:0.05 and 1:0.9, and typically about 1:0.09-1:0.7. By"di-functional" it is meant that each epoxy resin molecule includes onlytwo reactive oxirane moieties, and each 9,9-bis(hydroxyphenyl)fluorenemolecule includes only two reactive hydroxy groups.

The amount of curative used will depend on its degree of reactivity andin some instances its relative reactivity with respect to the fluorenecomponent. Generally, it should be selected and used in an amountsufficient or effective for reaction with a substantial amount ofremaining reactive oxirane moieties in the epoxy resin, i.e. those epoxyor oxirane moieties in excess of the reactive hydroxy-moieties on thefluorene component. The term "a substantial amount" as used herein, inthis context, is meant an amount sufficient to generate enoughcross-linking to result in a cured polymer having the desired Tg andtoughness. As an example, if a curative capable of reacting with 3oxirane units were selected, it could be used in a molecular ratio ofabout 2:3 with the excess epoxy resin; i.e. that amount of epoxy resinin excess over the fluorene component. It is noted that mixtures ofcuratives may be used, including mixtures of components having differingreactivities or available reactive sites for cross-linking. The term"curative" as used herein is meant to include mixtures of curatives.

The result of the above is generally improved cured resins. Also, theresin composition is made particularly susceptible to enhancements bytoughening agents. A reason for this may be that the lengths ofepoxy-chain units, or polymer backbone, between cross-links is generallyincreased, by comparison to non-improved resins. A result is that thepolymer can distort around the toughener, leading to better or enhancedincorporation of the toughener with resulting beneficial effectstherefrom.

In a typical process according to the present invention, the epoxy resincomposition is prepared and is heated to the appropriate curingtemperature, for a length of time sufficient to substantially completelycure the composition. Generally, preparation of the composition involvesa pre-dispersing of any toughening agent in the epoxide compound,followed by mixing of the resulting toughener/epoxide mix with the chainextension agent (i.e. the 9,9-bis(hydroxyphenyl)fluorene composition)and curative. Preferred compositions according to the present inventioncan be cured between the temperatures of about 50° C. and about 300° C.In conventional manners curing temperature cycles may be applied, tofacilitate curing in a desired manner and at a selected rate. Typically,it is desired to have complete curing within a time period of about 10minutes to 12 hours (overnight).

The cured resin may be effectively used as a bonding film or filmadhesive in a variety of applications. Typically, they will be used asadhesive films between first and second substrates, to form afilm/substrate arrangement. For example, the adhesive might be used toattach aluminum skins to an airplane framework. In general, the resincompositions can be readily applied as films, and then cured.Preferably, the bonding film is made about 0.0005-0.030 inches(0.001-0.007 cm) thick.

A typical polyepoxide usable in compositions according to the presentinvention is 2,2-bis-[4-(2,3-epoxypropoxy)phenyl]propane, compound IIbelow: ##STR2##

Upon curing in the presence of a fluorene composition according to thepresent invention, an epoxide resin including such units as III belowwill result. ##STR3##

By formula III, it is not meant to suggest that the cured resincomprises only alternating epoxy unit and fluorene unit, but rather thatboth are included in the cured resin, generally in the alternatingmanner. As indicated previously, a substantial amount of the epoxy resinoxirane units will have reacted to form crosslinking, as a result of thecurative. The amount of oxirane units linked to substitute fluorene maybe varied considerably. However generally, for typical applicationsabout 5-90%, and preferably about 9-50%, of the oxirane units will belinked to a substituted fluorene compound as indicated at III above.

DETAILED DESCRIPTION OF THE PREFERRED AND ALTERNATE EMBODIMENTS

As required, detailed embodiments of the present invention are describedin detail herein. It is to be understood, however, that the detailsprovided are only exemplary of the invention, which may be embodied invarious forms. Therefore, the specific details disclosed herein are notto be interpreted as limiting, but rather as a basis for the claims andas a representative basis for teaching one skilled in the art tovariously employ the present invention in virtually any appropriatesystem, arrangement or manner.

Preferred improved epoxy resin compositions according to the presentinvention include: polyepoxides or residue therefrom; a chain extensionagent composition, or residue therefrom (i.e. the fluorene-containingbisphenol component); tougheners; and, curative, or residue therefrom(curing agent and/or catalyst), as follows:

The Epoxide Constituent

For preferred compositions according to the present invention, theepoxide constituent comprises any of a variety of polyepoxides, and mayinclude mixtures. It will be understood that the scope of the terms usedherein in discussion of this component, and other components, in theresin composition are meant to include residues from reaction or partialreaction with other components to for polymeric structures. Polyepoxidesare well known. Preferred aromatic polyepoxides for use according to thepresent invention include: the polyglycidyl ethers of polyhydricphenols; glycidyl esters of aromatic carboxylic acids;N-glycidylaminobenzenes; and, glycidylaminoglycidyloxybenzenes.

Examples of N-glycidylaminobenzenes suitable for use in the epoxy resincompositions of the present invention include the di-and polyglycidylderivatives of: benzeneamine; benzene diamines; naphthylenamine; and,naphthylene diamines. Such compounds include:N,N-diglycidylbenzeneamine; N,N-diglycidylnaphthalenamine;1,4-bis(N-glycidylamino)benzene; and, 1,3-bis(N,N-glycidylamino)benzene.The polyglycidyl derivatives of aromatic aminophenols are described inU.S. Pat. No. 2,951,825, incorporated herein by reference. An example ofthese compounds is N,N-diglycidyl-4-glycidyloxybenzeneamine.

Aliphatic polyepoxides may also be used, and are well known. Mostpreferably, the aromatic polyepoxides used in resin compositionsaccording to the invention are the polyglycidyl ethers of polyhydricphenols. The preferred aliphatic epoxides are the diglycidylethers ofcyclohexane dimethanol.

The polyepoxides are exemplified by the following: vinyl cyclohexenedioxide; epoxidized mono-, di- and triglycerides; butadiene dioxide;1,4-bis(2,3-epoxypropoxy)benzene; 1,3-bis(2,3-epoxypropoxy)benzene;4,4'-bis(2,3-epoxypropoxy)diphenyl ether;1,8-bis(2,3-epoxypropoxy)octane; 1,4-bis(2,3-epoxypropoxy)cyclohexane;4,4'-bis(2-hydroxy-3,4-epoxybutoxy)diphenyl dimethyl methane;1,3-bis(4,5-epoxypentoxy)-5-chlorobenzene;1,4-bis(3,4-epoxybutoxy)-2-chlorocyclohexane; diglycidyl thioether;diglycidyl ether; 1,2,5,6-diepoxy-hexyne-3; and, 1,2,5,6-diepoxyhexane.Other usable epoxides are found in Handbook of Epoxy Resins, Lee andNeville, McGraw-Hill, New York (1967), and U.S. Pat. No. 3,018,262,incorporated herein by reference. Some compounds include epoxides listedin U.S. Pat. No. 3,298,998, incorporated herein by reference. Thesecompounds include:

bis[p-(2,3-epoxypropoxy)phenyl]cyclohexane;

2,2-bis[p-(2,3-epoxypropoxy)phenyl]norcamphane;

5,5-bis[(2,3-epoxypropoxy)phenyl]hexahydro-4,7-methanoindane;

2,2-bis[4-(2,3-epoxypropoxy)-3-methylphenyl]hexahydro-4,7-methanoindane;and,

2-bis[p-2,3-epoxypropoxy)phenyl]-methylene-3-methylnorcamphane.

The Chain Extension Agent

The chain extension agent usable according to the present invention is a9,9-bis(hydroxyphenyl)fluorene composition and preferably includes atleast one compound of the general formula IV, as follows: ##STR4##wherein: each R⁰ and R¹ is independently selected from substituentsnon-reactive with epoxy groups in the resin; for example: each R⁰ ispreferably independently selected from the group comprising hydrogen(H); the halogen (F, Cl, Br and I); linear or branched alkyl groupshaving 1-6 carbon atoms; phenyl-; nitro-; acetyl-; and trimethylsilyl-;and, each R¹ is independently selected from the group comprising:hydrogen (H), phenyl-; the halogens, and alkyl groups having 1-6 carbonatoms. The 9,9-bis(hydroxyphenyl)fluorene composition may include morethan one compound according to formula IV.

When it is herein said that R⁰ and R¹ "independently" selected, it ismeant that there is no requirement that all groups R⁰ all be the samegroup, or that all groups R¹ be the same group.

Examples of chain extension agents (bisphenol fluorenes) according toformula IV include:

9,9-bis(4-hydroxyphenyl)fluorene,

9,9-bis(3-methyl-4-hydroxyphenyl)fluorene,

9,9-bis(3-chloro-4-hydroxyphenyl)fluorene,

9,9-bis(3-ethyl-4-hydroxyphenyl)fluorene,

9,9-bis(3,5-dimethyl-4-hydroxyphenyl)fluorene,

9,9-bis(3,5-dichloro-4-hydroxyphenyl)fluorene,

2-iodo-9,9-bis(4-hydroxyphenyl)fluorene,

3-bromo-9,9-bis(4-hydroxyphenyl)fluorene,

1-chloro-9,9-bis(4-hydroxyphenyl)fluorene,

2-methyl-9,9-bis(4-hydroxyphenyl)fluorene,

2,6-dimethyl-9,9-bis(4-hydroxyphenyl)fluorene,

1,5-dimethyl-9,9-bis(4-hydroxyphenyl)fluorene,

2-fluoro-9,9-bis(4-hydroxyphenyl)fluorene,

1,2,3,4,5,6,7,8-octafluoro-9,9-bis(4-hydroxyphenyl)fluorene,

2,7-dinitro-9,9-bis(4-hydroxyphenyl)fluorene,

2-chloro-4-methyl-9,9-bis(4-hydroxyphenyl)fluorene,

2,7-dichloro-9,9-bis(4-hydroxyphenyl)fluorene,

2-acetyl-9,9-bis(4-hydroxyphenyl)fluorene,

2-chloro-9,9-bis(4-hydroxyphenyl)fluorene, and

2-t-butyl-9,9-bis(4-hydroxyphenyl)fluorene.

Mixtures of hydroxyphenyl fluorenes may be utilized as the chainextension agent, in compositions according to the present invention.Mixtures may be preferred in some instances because they often have amelting point that is lower than the melting point of an individualhydroxyphenyl fluorene, and thus facilitate curing of the epoxy resincomposition at a temperature lower than might otherwise be possible.

The amount of chain extension agent used in resin compositions accordingto the present invention may be varied somewhat. Preferably, the amountof chain extension agent used is based on the amount of reactive epoxidefunctionality in the polyepoxy resin, generally according to theformula: 1 reactive hydroxy equivalent or less ofbis(hydroxyphenyl)fluorene per equivalent of epoxide group present inthe polyepoxide component. A wide range is possible in applications ofthe present invention. A range of about 0.5 to about 0.9 is preferable,as it permits a significant amount of epoxide group to react incross-linking. A most preferred range of hydroxy equivalent to reactiveepoxy or oxirane equivalent is about 0.09-0.5. The term "hydroxyequivalent" when used with respect to the fluorene-containing bisphenolis meant to refer to equivalents of reactive hydroxy groups, i.e. the9-hydroxy groups. Reference to equivalents of epoxy group in thepolyepoxide is meant to refer to reactive epoxy groups.

Curing Agents and Catalysts (Curatives)

The epoxy curatives curing agents and/or catalysts suitable for use incompositions according to the present invention include thoseconventionally used for curing epoxy resin compositions and formingcross-linked polymer networks. Such agents include aliphatic andaromatic primary amines, for example: di(4-aminophenyl)sulfone;di-(4-aminophenyl)ether; and 2,2-bis(4-aminophenyl)propane. Suchcompounds also include aliphatic and aromatic tertiary amines such asdimethylaminopropylamine and pyridine, which may act as catalysts togenerate substantial cross-linking. Further, boron trifluoride complexessuch as BF₃ -monoethanolamine; imidazoles such as2-ethyl-4-methylimidazole; hydrazides such as aminodihydrazide;guanidines such as tetramethyl guanidine; and, dicyandiamide are usefulas curing agents or catalysts.

The amount of curing agent and/or catalyst needed will vary from resinto resin and is generally to be provided in such an amount as to beeffective in causing substantially complete curing within a desiredlength of time. A typical composition according to the present inventionincludes about 1-30%, by weight, of curing agent. It will be understoodthat the final properties of the cured resin composition will be greatlyinfluenced by the relative amounts of cross-linking and epoxy chainextension caused respectively by the curative and chain extension agent.Generally, this is set by selecting the amount of equivalents ofsubstituted fluorene(s) as the chain extension agent, and then using anappropriate amount of curative to achieve curing at a selected rate.

The Toughening Agent

Toughening agents for use in preferred compositions of the presentinvention generally comprise: elastomer molecules, separate elastomerprecursor molecules; combination molecules that include epoxy-resinsegments and elastomeric segments; and, mixtures of such separate andcombination molecules. The combination molecules may be prepared byreacting epoxy resin materials with elastomeric segments; the reactionleaving reactive functional groups, such as unreacted epoxy groups, onthe reaction product. The general use of tougheners in epoxy resins iswell-known, and is described in the Advances in Chemistry Series No. 208entitled "Rubbery-Modified Thermoset Resins", edited by C. K. Riew andJ. K. Gillum, American Chemical Society, Washington, 1984, the referencebeing incorporated herein by reference. The amount of toughening agentto be used depends in part upon the final physical characteristics ofthe cured resin desired, and is generally determined empirically. For atypical preferred embodiment, the toughening agent comprises 2-40% andpreferably about 4-20% by weight of the resin composition.

Some useful toughening agents include: carboxylatedacrylonitrile/butadiene vulcanizable elastomer precursors (such asHycar® CTBNX and Hycar® 1072, B.F. Goodrich Chemical Co.); butadienepolymer (Hycar® CTB, B.F. Goodrich Chemical Co.); amine functionalpolyethers such as: HC1101 (a 10,000 MW, primary amine-terminated,compound; Minnesota Mining and Manufacturing Co.; St. Paul, Minn.),Jeffamine® (Texaco Chemical Co.); and isocyanate-functional polyetherssuch as: Adiprene® (Uniroyal Chemical Co.); functional acrylic rubbersincluding acrylic core/shell material, such as Acryloid® KM330 and 334,Rohm & Haas; and core/shell polymers, such asmethacrylate-butadiene-styrene (MBS) copolymer wherein core iscross-linked styrene/butadiene rubber and shell is polymethylacrylate(Acryloid® KM653, Acryloid® KM680; Rohm and Haas).

As used above, for acrylic core/shell materials "core" will beunderstood to be acrylic polymer having Tg<0° C. and "shell" will beunderstood to be an acrylic polymer having Tg>25° C. Tougheners mayinclude epoxy-terminated compounds, which can be incorporated into thepolymer backbone.

A typical, preferred, list of tougheners comprises: acrylic core/shellpolymers; styrenebutadiene/methacrylate core/shall polymers; polyetherpolymers; carboxylated acrylonitrile/butadienes; and, carboxylatedbutadienes.

Advantages can be obtained from the provision of the chain extensionagent in a composition with an epoxy resin even in the absence of atoughening agent as described above. However, particular advantage isachieved from the presence of the toughening agent, as indicated byExample 2, and as previously suggested. It is a feature of the presentinvention that improved resins as disclosed herein are generally madeparticularly susceptible to, or are enhanced with respect to, thebeneficial effects of tougheners.

Adjuvants

Various adjuvants may be added to compositions according to the presentinvention, to alter the characteristics of the cured composition.Included among useful adjuvants are: thixotropic agents such as fumedsilica; pigments such as ferric oxide, brick dust, carbon black, andtitanium oxide; fillers such as silica, magnesium sulfate, calciumsulfate, and beryllium aluminum silicate; and, clays such as bentonite.Amounts of up to about 200 parts of adjuvant per 100 parts of epoxyresin composition may be effectively utilized.

Formation and Use of the Epoxy Resin Compositions

Generally, the toughening agent is pre-dispersed in the epoxidecompound. The toughener-containing epoxide is then mixed with a curativeand the chain extension agent to form a substantially uniform mixture.The mixture is cured upon heating for an appropriate length of time.While the curing reaction may take place slowly at room temperature, itis preferably brought about by heating the mixture to about 50° C. to150°-300° C. for an appropriate length of time. Often heating cycles maybe utilized, such as, for example, 50° C. for 0.25-1.0 hours, 150°-200°C. for 0.5-2.0 hour and 175°-250° C. for 1.0-5.0 hours.

In some instances it may be preferred to react all of the chainextension agent with the resin, before curing is initiated. This will,in part, depend on the percent of chain extension agent to beincorporated.

It is observed that compositions according to the present invention areparticularly advantageous, by comparison to the compositions of U.S.Pat. No. 4,684,678, when low percent chain extension agent is involved.Generally, this results from greater stability of the dihydroxy compoundrelative to the diamine.

The resin compositions of the invention are useful, for example: asstructural adhesives; as films or protective coatings for variousarticles such as appliances; as impregnating and embedding materials forelectrical components; and, in other uses, especially those wherein theoperating temperature of the article or material is expected to besubstantially elevated over room temperature.

The following examples illustrate specific embodiments and applicationsof the present invention. In all examples all parts and percents are byweight, and temperatures are in degrees Centigrade unless otherwisenoted. In the examples, the overlap shear strength and floating rollerpeel strength of cured resins is given. This is as determined anddescribed in ASTMD-3167-7b and MMM-A-132. Results are typicallycalculated in megapascals (MPa) and/or kilograms per centimeter (kg/cm).Peel strength and fracture energy relate to toughness and ductility inthat the higher the peel strength and fracture energy, the greater thetoughness of the material. This is interpreted herein as improvedtoughness or ductility.

EXAMPLE 1

The 9,9-bis(4-hydroxyphenyl)fluorene chain extension agent was preparedas follows:

A 500 ml 3-necked flask was equipped with a thermometer and means forintroducing hydrogen chloride. To the flask were added: 90.0 gfluorenone; 282.0 g phenol; and, 3.1 g 3-mercaptopropionic acid. Themixture was heated to 55° C., with stirring.

Anhydrous hydrogen chloride (9.0 g) was flushed through the reactionflask over about a 30 minute period. The mixture was reacted for about 6hours at 55° C., and was poured into 3 liters of methanol. Theprecipitate was collected and recrystallized from 1,2-dichloroethane toyield 130 g of white crystals, melting pt. 224.5°-225.5° C. Conventionalanalysis indicated that the crystals were9,9-bis(4-hydroxyphenyl)fluorene. This material is referred to herein asmonomer F.

EXAMPLE 2

Polymerization of an epoxy resin with 9,9-bis(4-hydroxyphenyl)fluorene.

To a resin flask fitted with a mechanical stirrer and a thermometer: 49g of diglycidyl ether of bisphenol A, epoxide (equivalent weight193-203) (Epon® 829, Shell Chemical Co.); and, 12.25 g9,9-bis(4-hydroxyphenyl)fluorene (monomer F), prepared as above, wereadded. The mixture was heated to about 121° C. with continuous

stirring, and was maintained at 115°-127° C. until a uniform mixture wasobtained, i.e. 15-30 minutes. Polytetramethylene oxide diprimary amine,12.5 g, Mw about 12,000 (HC 1101, 3M Co.), which had been melted atabout 82° C. was added slowly to the reaction flask with stirring. Themixture was heated at about 177°-204° C. for about 120 minutes, wasdumped and cooled at about 25° C. on silicone treated kraft paper, andwas then dissolved in an 85-15 mixture of methyl ethyl ketone andtoluene. This mixture is referred to herein as "Component A".

A "Component B" was prepared by milling together: 8.1 g of diglycidylether of bisphenol A, epoxide equivalent weight about 182-200 (Epon®828, Shell Chemical Co.); 4.5 g dicyandiamide (Aero®, American CyanamidCo.) and 1.8 g of a reaction product of toluenediisocyanate anddimethylamine (TDI Urea), on a 3-roll paint mill to a fineness of NS 4+.NS 4+ indicates a particle size≦0.005 cm. The grinding is done untilwhen film of the material is viewed at grazing incidence 5-10 particleswithin a 3 mm band appear through the surface.

The following were added to a double tite tin: 2.5 g Epon® 828; 10.0 gcondensation polymer of epichlorohydrin and Bisphenol A, epoxideequivalent weight about 230-280 (Epon® 834, Shell Chemical Co.); 12.25 g9,9-bis(4-hydroxyphenyl)fluorene; Component A; and, Component B. Adouble tite tin is a can having a friction top which seals against bothan inside and outside lip, for example a typical paint can. The mixturewas blended on a roller mill. For testing purposes a dry film wasprepared by coating the mixture on a silicone treated polyethylenecoated paper backing at a wet thickness of about 0.25 mm, with a dryingof the film for about 60 minutes at about 24° C. followed by treatmentfor about 60 minutes at 66° C. in a fresh air circulating oven. Thismaterial is identified herein as "Film A".

The shear strength was determined according to Federal Specification MMMA-132A and peel strength was determined according to ASTM D-3167-7busing 2024 T-3 aluminum panels which had been first degreased byexposing panel to hot (about 138° C.) vapors of perchloroethylene forabout 15-20 minutes, drying in air, immersing in alkaline degreaser("Oakite Aluminum Cleaner 164", Oakite Products Inc., Berkeley Heights,N.J.) at about 82° C. for about 10 minutes, and rinsing with tap waterand then deoxidized by immersing in a 71° C. bath of concentratedsulfuric acid, sodium dichromate and water for about 10 minutes (this isknown as Forest Lake Products Etch Systems or FPL Etch System) followedby rinsing with deionized water and finally anodized by immersion inphosphoric acid at 22° C. with applied voltage of 15 volts for 20-25minutes followed by rinsing with tap water (test for water break) andair drying 10 minutes at 22° C. and 10 minutes at 71° C. The total areato be bonded on both panels was primed with corrosion inhibiting primerfor aluminum (3M EC-3924B).

Glass transition temperature was determined using a DifferentialScanning Calorimeter (DSC). Test results are presented in Table I below.

For a comparative example, an adhesive film was analogously preparedusing Bisphenol A in place of Monomer F. In particular, using ananalogous procedure to that described above, a "Film B" was preparedusing the following:

    ______________________________________                                        Ingredient           Amount                                                   ______________________________________                                        Component A:  Epon ® 829                                                                           44.3 g                                                             Bisphenol A                                                                              8.0                                                                HC-1101    12.4                                                 Component B:  Epon ® 828                                                                           8.1 g                                                              Dicyandiamid                                                                             4.5                                                                TDI Urea   1.8                                                                Epon ® 828                                                                           7.2                                                                Epon ® 834                                                                           10.0                                                               Bisphenol A                                                                              8.0                                                  ______________________________________                                    

                  TABLE I                                                         ______________________________________                                                   Cure   Test                                                                   Temp.  Temp.    Test Results                                       Property     °C.                                                                             °C.                                                                             Film A Film B                                  ______________________________________                                        Tg(C)                          127.5  109.7                                   Peel (kg/cm) 135       22      13.0   12.9                                    Overlap Shear (MPa)                                                                        135       22      38.5   34.5                                     "                     94      26.1   18.8                                     "                    121      21.2   11.3                                     "                    149      13.7    3.0                                     "                    177       3.1    1.7                                    ______________________________________                                    

The data of Table I indicates the replacement of bisphenol A withMonomer F produces substantial increase in glass transition temperature(Tg), and hence a higher (improved) temperature performance, without adetraction from peel and shear strengths. That is, Monomer F results inhigher glass transition temperature without any high densitycross-linking. It is noted that at higher temperatures, improvement inshear strength (i.e. ductility) was observed.

EXAMPLE 3 Comparative Formulations

The following examples concern comparisons between formulations anddemonstrate increased Tg and ductility attainable using epoxycompositions of the present invention.

Six epoxy compositions were prepared using the formulations outlined inTable II below, by mixing the combined ingredients in a container andheating in an oven for 150° C. for about 30 minutes, followed by heatingat 177° C. for about 240 minutes. The six compositions are identified asA, B, C, D, E and "Ex. 2". "Ex. 2" is meant to refer to a composition asdefined in Example 2 above. The cured resins were allowed to cool at 25°C., were cut into suitable sample sizes and were tested for fractureene.gy, determined by compact tension according to ASTM E399-83. Theywere also tested for glass transition temperature (Tg), as measured byDifferential Scanning Calorimeter. The results were as follows:

                                      TABLE II                                    __________________________________________________________________________                      Monomer                                                                             Bisphenol      Fracture                                      Epoxy.sup.(1)                                                                      Curative.sup.(2)                                                                    F.sup.(3)                                                                           A.sup.(4)                                                                           Toughener                                                                           Tg Energy                                        Eq.  NH Eq.                                                                              OH Eq.                                                                              OH Eq.                                                                              Wt. %.sup.(5)                                                                       °C.                                                                       J/m.sup.2                              __________________________________________________________________________    Comp. Ex. A                                                                          0.5  0.5                     208                                                                               65                                    Comp. Ex. B                                                                          0.5  0.25  0.25              185                                                                              190                                    Comp. Ex. C                                                                          0.5  0.25        0.25        137                                                                              180                                    Comp. Ex. D                                                                          0.5  0.5               5     204                                                                              120                                    Ex. 2  0.5  0.25  0.25        5     183                                                                              1600                                   Comp. Ex. E                                                                          0.5  0.25        0.25  5     136                                                                              1850                                   __________________________________________________________________________     .sup.(1) 2,2bis[4(2,3epoxypropoxy)phenyl]propane                              .sup.(2) diaminodiphenylsulfone                                               .sup.(3) 9,9bis(4-hydroxyphenyl)fluorene, OH eq. wt. 175                      .sup.(4) OH eq. wt. 114                                                       .sup.(5) KM 653, Rohm and Haas Co., Philadelphia, Pa. This substance is a     core/shell copolymer of polymethacrylate rigid shell with an elastomeric      core of crosslinked styrene/butadiene.                                   

Table II demonstrates several embodiments of the invention. The additionof the diphenol in B and C demonstrates that the use of chain extensionagent (Monomer F or bisphenol A) in place of a portion of the curativeused in comparative Example A will significantly increase the toughnessof the cured resin, see Comparative Examples B and C. However, whenbisphenol A is used as a chain extension agent (Comparative Example C),a drastic and undesirable reduction in the glass transition temperatureresults. When the fluorene bisphenol, Monomer F, is used the toughnessis increased as much as it was for bisphenol A; but a much higher glasstemperature results.

The data also demonstrates the beneficial effects of the addition of arubber toughening agent to the epoxy compositions. When a tougheningagent was added to the highly cross-linked composition (ComparativeExample D), the improvement in toughness energy was minimal. However,when the toughener was added to the chain-extended compositions, theeffect on toughness was much more pronounced, see Example 2 andcomparative Example E. Again, when Monomer F was used as the chainextension agent, the glass transition temperature is much higher thanwhen bisphenol A was used.

Further General Statements of the Invention

From the previous examples, it will be understood that generallyaccording to the present invention an improvement in cured product of anepoxy resin is accomplished through provision of a chain agent in theepoxy resin composition to be cured or cross-linked. Specifically,improvement is obtained through the utilization of a9,9-bis(hydroxyphenyl)fluorene compound, as the chain extension agent.The improvements generally relate to improvement in glass transitiontemperature (i.e. raising of glass transition temperature) withoutsubstantial loss of toughness or ductility, or improvement in Tg withoutany substantial loss of toughness. In many instances both Tg andtoughness can be improved.

Significantly, the present invention also involves improvement throughprovision, in addition to the chain extension agent, of a tougheningagent in the resin composition. As illustrated in Table II, asignificant overall improvement is achieved in both the9,9-bis(hydroxyphenyl)fluorene and the toughening agent are present.

In addition to a method of improving the epoxy resin compositions, orthe physical characteristics of cured epoxy resin compositions, thepresent invention also concerns a particular, preferred, epoxy resincomposition according to the above general features.

It is to be understood that while certain embodiments of the presentinvention have been illustrated and described, the invention is not tobe limited to the specific forms, compositions, systems or proceduresherein described and/or illustrated.

What is claimed and desired to be secured by Letters Patent is asfollows:
 1. A method of improving a glass transition temperature andductility of a cured product from an epoxy resin composition; saidmethod including the step of:(a) providing in said epoxy resincomposition an effective amount of a 9,9-bis(hydroxyphenyl)fluorenecomposition; said 9,9 bis(hydroxyphenyl)fluorene composition beingprovided in an amount of between about 0.09 and 0.7 hydroxy equivalentsof 9,9-bis(hydroxyphenyl)fluorene composition per equivalent of reactiveepoxide group in a polyepoxide component from which said resincomposition is formed.
 2. The method according to claim 1 including:(a)providing in said epoxy resin composition an amount of curativeeffective to generate cross-linking by means of reacting a substantialamount of those reactive epoxide groups in said polyepoxide component inexcess of the amount of hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene.
 3. The method according to claim 2wherein:(a) said curative includes an epoxide curing agent having atleast 3 reactive sites for reaction with reactive oxirane groups in saidpolyepoxide component.
 4. The method according to claim 1 wherein said9,9-bis(hydroxyphenyl)fluorene composition includes at least onecompound according to the formula: ##STR5## wherein: each R⁰ isindependently selected from hydrogen and other groups substantiallyinert to the polymerization of epoxide group-containing compounds; and,each R¹ is independently selected from hydrogen and other groupssubstantially inert to the polymerization of epoxide group-containingcompounds.
 5. The method according to claim 4 wherein: each R⁰ isindependently selected from the group comprising: hydrogen; thehalogens; alkyl groups having 1-6 carbon atoms; phenyl; nitro; acetyl;and, trimethylsilyl; and, each R¹ is independently selected from thegroup comprising: hydrogen; phenyl; the halogens; and, alkyl groupshaving 1-6 carbon atoms.
 6. A method of improving a glass transitiontemperature and ductility of a cured product from an epoxy resincomposition; said method including the steps of:(a) providing in saidepoxy resin composition an effective amount of a9,9-bis(hydroxyphenyl)fluorene composition; and, (b) providing atoughening agent in said epoxy resin composition; said toughening agentbeing selected from the group consisting of: acrylic core/shellpolymers; styrene-butadiene/methacrylate core/shell polymers; polyetherpolymers; carboxylated acrylonitrile/butadienes; carboxylatedbutadienes; and mixtures thereof.
 7. A resin composition comprising:(a)a polyepoxide resin; and (b) between about 0.09 and 0.7 hydroxyequivalents of a 9,9-bis(hydroxyphenyl)fluorene composition.
 8. A resincomposition according to claim 7 including a curative effective togenerate cross-linking by means of reacting a substantial amount ofthose reactive epoxide groups in said polyepoxide component in excess ofthe amount of hydroxy equivalents of 9,9-bis(hydroxyphenyl)fluorene. 9.The resin composition according to claim 7 including a curativecomprising an epoxide curing agent having at least 3 reactive sites forreaction with reactive oxirane groups in said polyepoxide component. 10.A resin composition according to claim 7 including:(a) at least oneelastomer toughening agent.
 11. The resin composition according to claim7 wherein said 9,9-bis(hydroxyphenyl)fluorene composition includes atleast one compound according to the formula: ##STR6## wherein: each R⁰is independently selected from hydrogen and other groups substantiallyinert to the polymerization of epoxide group-containing compounds; andeach R¹ is independently selected from hydrogen and other groupssubstantially inert to the polymerization of epoxide group-containingcompounds.
 12. The resin composition according to claim 11 wherein: eachR⁰ is independently selected from the group comprising: hydrogen; thehalogens; alkyl groups having 1-6 carbon atoms; phenyl; nitro; acetyl;and, trimethylsilyl; and, each R¹ is independently selected from thegroup comprising: hydrogen; phenyl; the halogens; and, alkyl groupshaving 1-6 carbon atoms.
 13. A resin composition comprising:(a) apolyepoxide resin; (b) between about 0.05 and 0.9 hydroxy equivalents ofa 9,9-bis(hydroxyphenyl)fluorene composition; and (c) at least onetoughening agent selected from the group consisting of: acryliccore/shell polymers; styrene-butadiene/methacrylate core/shell polymers;polyether polymers; carboxylated acrylonitrile/butadienes; carboxylatedbutadienes; and, mixtures thereof.
 14. A composition according to claim13 including between about 0.09 and 0.7 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition.
 15. A method of providing animproved cured resin; said method including steps of:(a) providing anepoxy resin composition including:(i) a curable polyepoxide resin; (ii)between 0.09 and 0.7 hydroxy equivalents of a 9,9-bis(hydroxyphenyl)fluorene composition per equivalent of reactive epoxide group in thepolyepoxide resin; and (iii) a curing agent; and (b) curing said epoxyresin composition.
 16. The method according to claim 15 wherein:(a) said9,9-bis(hydroxyphenyl)fluorene composition includes at least onecompound according to the formula: ##STR7## wherein: each R⁰ isindependently selected from hydrogen and other groups substantiallyinert to the polymerization of epoxide group-containing compounds; andeach R¹ is independently selected from hydrogen and other groupssubstantially inert to the polymerization of epoxide group-containingcompounds.
 17. The method according to claim 16 wherein: each R⁰ isindependently selected from the group comprising: hydrogen; thehalogens; alkyl groups having 1-6 carbon atoms; phenyl; nitro; acetyl;and, trimethylsilyl; and, each R¹ is independently selected from thegroup comprising: hydrogen; phenyl; the halogens; and, alkyl groupshaving 1-6 carbon atoms.
 18. The method according to claim 15wherein:(a) said epoxy resin includes an elastomer toughening agent. 19.An improved cured resin formed according to the method of claim
 16. 20.An improved cured resin formed according to the method of claim
 17. 21.An improved cured resin formed according to the method of claim
 18. 22.An improved cured resin formed according to the method of claim
 15. 23.A method of improving glass transition temperature and ductility of acured product from an epoxy resin composition; said method including thestep of:(a) providing in said epoxy resin composition an effectiveamount of a 9,9-bis(hydroxyphenyl)fluorene composition; said9,9-bis(hydroxyphenyl)fluorene composition being provided in an amountof between about 0.05 and 0.7 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition per equivalent of reactiveepoxide group in a polyepoxide component from which said resincomposition is formed.
 24. A method of improving glass transitiontemperature and ductility of a cured product from an epoxy resincomposition; said method including the step of:(a) providing in saidepoxy resin composition an effective amount of a9,9-bis(hydroxyphenyl)fluorene composition; said9,9-bis(hydroxyphenyl)fluorene composition being provided in an amountof about 0.05 to less than 0.9 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition per equivalent of reactiveepoxide group in a polyepoxide component from which said resincomposition is formed.
 25. A method of improving a glass transitiontemperature and ductility of a cured product from an epoxy resincomposition; said method including the steps of:(a) providing in saidepoxy resin composition an effective amount of9,9-bis(hydroxyphenyl)fluorene composition; and, (b) providing anelastomer toughening agent in said epoxy resin composition.
 26. Themethod according to claim 24 wherein said epoxy resin compositionincludes between about 0.09 and 0.7 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition per equivalent of reactiveepoxide group.
 27. The method according to claim 24 wherein said9,9-bis(hydroxyphenyl)fluorene composition includes at least onecompound according to the formula: ##STR8## wherein: each R⁰ isindependently selected from hydrogen and other groups substantiallyinert to the polymerization of epoxide group-containing compounds; and,each R¹ is independently selected from hydrogen and other groupssubstantially inert to the polymerization of epoxide group-containingcompounds.
 28. A resin composition comprising:(a) a polyepoxide resin;and, (b) about 0.05 to less than 0.9 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition.
 29. A resin compositionaccording to claim 28 including about 0.05 to 0.7 hydroxy equivalents ofthe 9,9-bis(hydroxyphenyl)fluorene composition.
 30. A resin compositioncomprising:(a) a polyepoxide resin; (b) between about 0.05 and 0.9hydroxy equivalents of 9,9-bis(hydroxyphenyl)fluorene composition; and,(c) an elastomer toughening agent.
 31. A composition according to claim30 including between about 0.09 and 0.7 hydroxy equivalents of9,9-bis(hydroxyphenyl)fluorene composition.
 32. A method of providing acured product, from an epoxy resin composition, having improved glasstransition temperature and ductility; said method including steps of:(a)providing in said epoxy resin composition an effective amount of unitsaccording to the general formula: ##STR9## wherein: each R⁰ and R¹ isindependently selected from hydrogen and other groups substantiallyinert to polymerization of epoxide group-containing compounds; and, (b)providing in said epoxy resin composition an elastomer toughening agent.33. The method according to claim 32 wherein:(a) each R⁰ isindependently selected from the group comprising: H; the halogens;linear and branched alkyl groups having 1-6 carbon atoms; phenyl groups;nitro groups; acetyl groups; and, trimethylsilyl groups; and, (b) eachR¹ is independently selected from the group comprising: H; phenyl; thehalogens; and linear and branched alkyl groups having 1-6 carbon atoms.34. The method according to claim 32 wherein the provided elastomertoughening agent is selected from the group consisting of: acryliccore/shell polymers; styrenebutadiene/methacrylate core/shell polymers;polyether polymers; carboxylated acrylonitrile/butadienes; carboxylatedbutadienes; and, mixtures thereof.